The Application Of Microseismic Monitoring In Shale Well Fracturing Of Sourthern Sichuan

The exploration and development technology for non-conventional reservoirs such as shale gas is becoming a hot pot in the field of current global oil and gas resources.The shale gas is abundant in China,especially Sichuan-Chongqing region has the largest scale of the country,however the relevant exploration and development work is still in its infancy.Shale gas reservoirs are often referred to as “artificial gas reservoir”,exploration and development often need horizontal drilling and hydraulic fracturing technology to transform the reservoir in order to form an artificial fracture network of industrial production capacity.The current development in southern Sichuan always using multi-stage volume fracturing in horizontal wells,compared to conventional fracturing methods,the formation of fracture networks is more complex,and the situation of fracturing is more complicated.Conventional fracturing monitoring techniques,such as pressure analysis,temperature logging,radioactivity testing,etc. can not fully meet the monitoring of large hydraulic fracture formation process for its limitations.As an emerging geophysical technology,micro-seismic monitoring the effect of fracturing and underground status changes by observing the acoustic emission of rock cracking during hydraulic fracturing.It monitor micro-seismic signal from underground through the detector laid in nearby well or arranged on the ground,and get source information about the event(spatial distribution,magnitude size),in order to assess the morphological characteristics of the entire fracture network.This paper describes the basic principles of micro-seismic system and fundamental processes methods of well monitoring using a typical large hydraulic fracturing of a well group platform in Southern Sichuan.It mainly includes:geometry designing and signal acquisition method based on well conditions and parameters of fracturing,access to high-quality micro-seismic signals,analyze micro-seismic signals and background noise in different intensities.Different from the conventional seismic processing,apply its own preprocessing techniques,polarization analysis,velocity modeling and correction method,and source-velocity joint inversion technology in inhomogeneous media,to achieve the precise positioning of micro-seismic events,with the average error control in less than 15 m.Apply micro-seismic technology to monitor the large-scale hydraulic fracturing,getting a good effect.Real-time processing results give a preliminary evaluation of the effect of fracturing and recommendations to parameter adjustment,reducing the operating costs effectively,avoiding the fracturing problems successfully.After fracturing,interpreter the result using geological,fracturing and seismic data,describe the fracture network using the time properties and energy properties of micro-seismic events,to get the information of Stimulated Reservoir Volume(SRV),to provides a great deal of basic data for the latter part of reservoir description and development work.Finally,this paper discusses the basic flow of micro-seismic monitoring using surface array, and compares the result with the well result.It proves that monitoring using surface array can describes the network basically when there is no apposite observation well.